SPECIAL RELATIVITY BASICS

Question 1

postulates of SR

Answer 1

laws of physics are invariant
speed of light is constant

Question 2

time dilation formula

Answer 2

delta t = gamma * proper time

Question 3

proper time

Answer 3

the shortest time possible between 2 events

Question 4

what frame does proper time occur in?

Answer 4

the frame in which A and B occur in the same location

Question 5

length dilation

Answer 5

proper length = L * gamma

Question 6

proper length

Answer 6

largest length possible

Question 7

what frame is proper length measured in

Answer 7

frame where events happen at the same time

Question 8

lorentz invariants

Answer 8

(delta s )^2

c

Question 9

when to use lorentz transformation

Answer 9

when we know the space time coordinates in one frame and want to find them in the other

Question 10

space time interval

Answer 10

(delta s)^2 = (c delta t)^2 - (delta x)^2 - (delta y)^2 - (delta z)^2

Question 11

spacelike events

Answer 11

travels more in space than time

shallower line

space time interval squared < 0

Question 12

timelike

Answer 12

travels more in time than space

steeper line

space time interval squared > 0

Question 13

light like

Answer 13

travels at c
y = x
spacetime interval = 0

Question 14

events in the undefined region of a light cone

Answer 14

to get to these, you would have to travel faster than c

they can be observed as we wait for the light to travel to us

Question 15

causally linked

Answer 15

negative spacetime interval

lots of time but little space between events

Question 16

velocity addition fromula

Answer 16

u’ = u - v / 1 - uv/c^2

Question 17

experimental evidence supporting SR

Answer 17

• due to time dilation, muons will have a longer lifetime if they are moving
• in particle accelerators, particles also have a lifetime that increases with speed
• doppler effect

Question 18

what is conserved in frames throughout SR

Answer 18

energy and momentum

Question 19

invariants VS conserved quantities

Answer 19

invariants have the same value throughout all reference frames eg c and (mc^2)^2 and delta s squared

some quantities are conserved in all frames, but have different values in different frames
eg E and p

Question 20

energy equation

Answer 20

E^2 - (pc)^2 = (mc^2)^2

total energy squared - pc squared = rest energy squared

Question 21

inelastic collisions

Answer 21

E and p are conserved

total energy = gamma mc^2 = EK + mc^2

momentum = gamma m u

Question 22

photons

Answer 22

photons have no mass
light like as they travel at c
spacetime interval squared = 0
(c delta t)^2 = (delta x)^2
total energy squared - (pc)^2 = 0
E = pc